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Topic Review (Newest First)

03-28-2014 01:46 PM

cdminter59

67 396 valve job. Not sure about Machine Shops Answer

Dom, I am thinking that your pistons are the old seal power or speed pro domed pistons. They probably have a piston head volume of -21.00. If I run some figures thru the KB calculator https://www.uempistons.com/index.php...tors&type=comp) with your 98cc heads I get 10.254 for the Static Compression Ratio. You definitely would have to mix racing gas to keep from detonating. With either of the aluminum heads you could run 93 octane pump gas. With the GM heads and a .027 thick head gasket you would have 9.155 S.C.R. You could use 87-91 octane gas. Edelbrock 100cc chamber heads would give you 10.051 S.C.R. which you would still run 93 octane pump gas. BTW you would have to choose a new cam with an intake closing point to give you a 8.2- 8.5 DCR. Your quench on your engine is probably .054-.066 which isn't good. Most engine builders set the quench at .035-.045. You mill the top of the block and choose the right thickness head gaskets to get this.

03-27-2014 02:18 PM

BuzzLOL

. BTW, the bigger chamber heads can be milled to make them smaller chambers...

03-27-2014 12:59 PM

Dom L

Thank you all !

You all hava been hugely helpful !
At this poing, the can of worms will remain closed and after new guides & seats, it's going back together to enjoy for a few more years.

Thany you all again !
Dom

03-27-2014 12:56 PM

Dom L

Quote:

Originally Posted by BOBCRMAN@aol.com

One of the pitfalls of building a 396 based engine is the lack of availability of small chamber heads. The aftermkt is supplying heads based on the 112-122 big bore chambers. The 396 requires the small chambers to make compression/power. Larger chambers on a small bore require huge domes that then screw up flame travel and open up another separate can of worms.

Take a lesson from small block engines.. 76 chamber/big dome vs. 58 chamber/flat top pistons. Same approx. compression ratio, but different fuel/air/timing requirements.

Eventually, I will go bigger. For now, as buzz suggested, I'm going to put it back together and enjoy it. That will give me more time to build a 454 correctly sometime in the future.
Thank you !

03-27-2014 12:54 PM

Dom L

Quote:

Originally Posted by BuzzLOL

. Yes, you lose compression ratio, MPG, and possibly power with bigger cc heads, depending on how well the new heads flow air... and whether 'fast burn' combustion chambers... but bigger chambers may allow running on lower priced pump gas instead of race or boosted gas...

. So far, you really don't know what you're comparing... would need to get an itemized list of just what the guy will do for X price... just because he's slow in winter doesn't mean he doesn't know what he is doing... although it's often good to ask where your buddies went and if they are satisfied...

. And, like you say, if it's running OK for now, passes compression gauge testing, no oil smoke, not fouling plugs, maybe let it go for a few more years... just enjoy it...

I am leaning more and more in that direction. New guides and seats whick should include the valve job (It's a 67) and let it go at that.

03-27-2014 12:01 PM

BuzzLOL

. Yes, you lose compression ratio, MPG, and possibly power with bigger cc heads, depending on how well the new heads flow air... and whether 'fast burn' combustion chambers... but bigger chambers may allow running on lower priced pump gas instead of race or boosted gas...

. So far, you really don't know what you're comparing... would need to get an itemized list of just what the guy will do for X price... just because he's slow in winter doesn't mean he doesn't know what he is doing... although it's often good to ask where your buddies went and if they are satisfied...

. And, like you say, if it's running OK for now, passes compression gauge testing, no oil smoke, not fouling plugs, maybe let it go for a few more years... just enjoy it...

03-27-2014 11:51 AM

BOBCRMAN@aol.com

One of the pitfalls of building a 396 based engine is the lack of availability of small chamber heads. The aftermkt is supplying heads based on the 112-122 big bore chambers. The 396 requires the small chambers to make compression/power. Larger chambers on a small bore require huge domes that then screw up flame travel and open up another separate can of worms.

Take a lesson from small block engines.. 76 chamber/big dome vs. 58 chamber/flat top pistons. Same approx. compression ratio, but different fuel/air/timing requirements.

03-27-2014 11:04 AM

Dom L

Quote:

Originally Posted by oldbogie

Don't know where you live but if that's 530 dollars just for shooting 16 seats at 3 angles that's about twice the price. If it includes 16 new guides and 8 exhaust hard seats plus cleaning and magnaflux it's actually a darn good price.

Bogie

Bogie:
Would you be able to explain a little for me ?
cminter59 uggested newer heads. My understanding is/was, if I change the cc's from my original 98.4 to 11_ whaterver, I would be losing compression.
I can understand that. But, is that true ? Or, can I go with a set of heads with a higher number of cc's ?

Anyone else's comments are most certainly welcome also.

Thanks,
Dom

03-24-2014 02:29 PM

oldbogie

Quote:

Originally Posted by Dom L

Hi all.
Had the heads from my 67 396 to a machine shop for a price on valve seats and/or guides. Price for the 3 angle valve job is $ 530.00. New seats, $ 30 - 40 per. His suggestion was to only change the exhaust side.
I don't really know where to go with this. Any suggestions are greatly appreciated.
Thanks,
Dom

Don't know where you live but if that's 530 dollars just for shooting 16 seats at 3 angles that's about twice the price. If it includes 16 new guides and 8 exhaust hard seats plus cleaning and magnaflux it's actually a darn good price.

Bogie

03-24-2014 01:43 PM

Dom L

Quote:

Originally Posted by vinniekq2

I would leave the worms in a can,,,

I think I'm going to leave this can closed ! lol

03-24-2014 01:43 PM

Dom L

Quote:

Originally Posted by cdminter59

Dom, Check out these new aluminum heads from GM Parts Direct. They have 110 cc semi-open chambers. Also the valves are 2.19/1.88. GM Parts Direct: Search results The only other manufacturer that has a 100 cc chamber is Edelbrock 350-604719 from Jegs. The only problem I see is you don't know what camshaft you have to get the right springs. Take the camshaft out inspect it for part numbers if none take it to a machine shop to be measured.

As vinnykg2 suggests, I think I'm going to leave the can of worms closed.
The engine worked well before I put it to sleep and it's getting more and
more expensive to wake up. I think I'm going to do the least that I can, but make sure it's reliable, and wait on going bigger.

Thank you for the GM site. It is a very good site to look through.
I'll save it for hopefully going bigger in the future.
Dom

03-24-2014 01:05 PM

vinniekq2

I would leave the worms in a can,,,

03-24-2014 12:26 PM

cdminter59

67 396 valve job. Not sure about Machine Shops Answer

Dom, Check out these new aluminum heads from GM Parts Direct. They have 110 cc semi-open chambers. Also the valves are 2.19/1.88. GM Parts Direct: Search results The only other manufacturer that has a 100 cc chamber is Edelbrock 350-604719 from Jegs. The only problem I see is you don't know what camshaft you have to get the right springs. Take the camshaft out inspect it for part numbers if none take it to a machine shop to be measured.

03-22-2014 04:45 PM

Dom L

Quote:

Originally Posted by vinniekq2

offer 112cc heads. what size are you looking for?
another by product of buying brand new aluminum heads
less weight
more power

hope thats not a problem?

Would love to have aluminum heads. Especially if I could keep the compression.
The heads I have now are 98.427cc with domed pistons, which keeps the compression up.
More cc's will lower it. And, I would have to take the whole thing apart
to see what else is in there. Over my head and maybe my budget.

03-22-2014 04:37 PM

Dom L

Quote:

Originally Posted by tresi

This is a busy time of year for a good machine shop. People have their tax refund in hand an want to get their race motors done. If he has time to set around give him some more time to set around by finding another shop. Even are local parts store that sen all of their machine work off to it's corporate machine shop an hour and a half away would give you a better deal.

Tresi:
thanks !
I am going to return the valve spring compressor I borrowed from
my local store and will ask them.
Dom

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